A stiffer firearm barrel will typically be more accurate than one that exhibits inordinate flexing. A firearm barrel having a thicker wall will typically provide a stiffer barrel compared to one with a thinner wall. That is, for a given bore diameter, the larger the outside diameter of the barrel, the stiffer the barrel will be. Of course, thick-walled gun barrels can add significant weight to the firearm. In an effort to gain the benefit of a larger diameter and thicker-walled barrel, yet reduce its overall weight, flutes or groves have been formed along the length of the outer surface of the barrel. These flutes reduce the weight of the barrel while increasing the exterior surface area of the barrel, which can provide more effective cooling of the barrel.
The fluting grooves are typically formed in a longitudinal direction substantially parallel to the bore or, as described in U.S. Pat. No. 6,324,780, issued Dec. 4, 2001, to Carl H. Behling may be cut helically or spirally, if desired. In either style, the depth and width of each flute remains substantially constant along the length of the barrel, except at the terminal ends of each flute.
Another method for treating the exterior surface of a firearm barrel is disclosed in U.S. Pat. No. 7,013,592, issued Mar. 21, 2006, to Douglas D. Olson, et al. This patent teaches having a longitudinal portion of the barrel peripheral surface covered with an array of concaved circular or oblong depressions (dimples) machined in the peripheral surface to a predetermined maximum depth. As with the longitudinal and spiral groove fluting, the circular or oblong concave depressions are disclosed to reduce the weight of the barrel while retaining the barrel's original stiffness and to increase surface area to enhance heat dissipation.
Spiral fluting involves complex machining equipment and processes. Longitudinal fluting creates straight line edges parallel to the bore that may affect the stress performance of the barrel material. The depth and diameter of circular or oblong dimpling, and therefore its effectiveness, is limited on a cylindrical member like a barrel.